BOSTON (Reuters) - Days after surveillance video from the 1990 Stewart Gardner Museum heist was made public, FBI officials on Tuesday said they are investigating a "handful of tips," including one identifying a mystery man let in to the museum the night before it was robbed of $500 million worth of art.

Attorney George Burke of Quincy, Massachusetts, about 10 miles (16 km) outside Boston, said he told federal authorities one of his client identified the grainy video’s mystery man as a businessman who dealt in antiques, the same job held by the client. The two men worked together in the 1990s, Burke said.

The video shows a security guard letting the mystery man through a rear museum entrance on March 17, 1990. Twenty-four hours later it was robbed of works such as Rembrandt's "Storm on the Sea of Galilee," Vermeer's "The Concert" and Manet's "Chez Tortoni” in the biggest art heist in U.S. history.

Burke's client said the businessman in the video is alive in Florida, the former prosecutor said. Burke said he gave U.S. Attorney Carmen Ortiz the man’s Florida address and Ortiz’s office confirmed all information from Burke has been passed to the FBI.

Burke, a former district attorney, said the tipster has not identified himself because he “fears for his life."

Thirteen pieces of art were snatched on March 18, 1990, when overnight security guards let two men, dressed as Boston police officers, into the museum. The guards were found duct-taped to chairs in the museum’s basement the next day.

Authorities now have a "certain degree of confidence" that they have identified the two men disguised as police and they are now dead, FBI spokeswoman Kristen Setera said.

FBI officials from the Boston office said they released the video last week in the hopes it could lead to the stolen art.

"We are re-examining the case, just to see if we can turn up any new leads," FBI spokesperson Kristen Setera said on Tuesday. “We want to find the art."

The statute of limitations on the crime has long passed, meaning that if the thieves are found they will not face prosecution. But the FBI, the Boston office of the Justice Department and the museum hope to recover the art.